Now that Russia is tending not to be seen as a threat by the US there may be fewer US SSNs in the Atlantic Ocean facing Russian SSNs and Russian SSBNs, in the medium-long term. The Atlantic US SSNs may be relocated, with the main US SSN effort being against China (in the Pacific and Indian oceans) and against North Korea.
Whether Russian Pacific Fleet SSBNs, SSGNs and SSNs work in alliance to the Chinese submarine fleet is another uncertainty.
But as US forces and reliability as an ally desert Europe, the Russian threat is rising against the UK, France and the rest of Non US (NUS) NATO.
The age old Russian Intelligence aim of splitting the Western, especially NATO, alliance is succeeding under Putin, a former KGB officer and FSB boss.
The splitting off of the US from NATO, might make accelerated production of SSNs and SSBNs for the French Navy and also UK Royal Navy a high priority.
Instead of the planned 6 x SSNs of the Suffren class for France and 7 Astutes for the UK Royal Navy 2 more might be built of each.
The main job of these SSNs are to protect their own navy's SSBNs (leaving and entering port and maybe on patrol). Whether the rolling average of 4 SSBNs in each of the French and UK navies increases is unknown. The 4 new ones planned are the 4 x SNLE-3Gs and 4 x Dreadnoughts.
The reason Britain owns its current Vanguard-class SSBNs are as nuclear weapon platforms. But troublingly the warheads rely on regular US Tritium injections and the warhead guidance systems come from the US. Meanwhile the "UKs" Trident missiles are rented/leased from the US and the Trident's regular maintenance only takes place at King's Bay in the US. So Britain really needs total Trident system autonomy to operate in Trump's Russian influenced brave new world.
At least France's SSBNs, M51 nuclear missiles and M51.1 TNO nuclear warheads are not reliant on a senior ally.
What all this means for Australia's possible basing of US SSNs in Australia (low likelihood of UK SSNs being based here) and Australian SSN acquisition from the US, the UK or France, is difficult to predict.
France's increasing need to strengthen its own SSN defences against Russia means French SSNs for any foreign customer is very unlikely. But this does not preclude France from renewing the conventional Shortfin Barracuda Block 1A (Attack-class) deal with Australia.
Russia, unopposed by the US, threatens Russia's European west and also Russia's Siberian east. The latter may present a higher threat to other countries (South Korea and Japan) that might conceivably supply conventional subs to Australia. This may now make South Korea and Japan hesitant to supply submarines (conventional or, in future, nuclear) to Australia.